Fiber bonding process

ABSTRACT

Bonded fiber fabrics are produced by a process which comprises applying normally liquid sulfolanyl ether to a web of fibers selected from the group consisting of modified polyacrylonitrile fibers, cellulose ester fibers and chlorofibers, and heating the web and the sulfolanyl either to effect bonding of the fibers.

Elited States atent Inventors John C. Moseley Waking;

Rupert E. Schaifer, Camberly, both of England Dec. 8, 1969 Oct. 26, 1971 Shell Oil Company New York, N.Y.

Dec. 9, 1968, May 21, 1969 Great Britain Appl. No. Filed Patented Assignee Priorities FIBER BONDING PROCESS 9 Claims, No Drawings Int. Cl Field of Search Primary Examiner-Reuben Epstein Attorneys-John l-l. Colvin and E. Walter Mark ABSTRACT: Bonded fiber fabrics are produced by a process which comprises applying normally liquid sulfolanyl ether to a web of fibers selected from the group consisting of modified polyacrylonitrile fibers, cellulose ester fibers and chlorofibers, and heating the web and the sulfolanyl either to effect bonding of the fibers.

FIBER BONDING PROCESS This invention relates to the production of bonded fiber fabrics. Bonded fiber fabrics are understood herein to be fabrics consisting of a web of staple fibers bonded together. The invention particularly relates to production of bonded fiber fabrics in which the fibers are fibers from copolymers of acrylonitrile and another organic compound containing at least one ethylenically unsaturated carbon-carbon bond, such as vinyl chloride, vinylidene chloride, vinyl pyrrolidone, vinyl pyridine, vinyl acetate, methyl acrylate or methyl methacrylate. Whenever such copolymers contain from 30 to 90 percent by weight of acrylonitrile units and 70 to percent by weight of units of one or more of the said unsaturated compounds, these copolymers are referred to hereinafter with generic term modified polyacrylonitrile." The invention also relates to the production of bonded fiber fabrics in which the fibers are cellulose ester fibers or chlorofibers which are understood herein to be fibers made from homopolymers or copolymers of vinylchloride or vinylidene chloride. The comonomer in said copolymers can be any ethylenically unsaturated compound other than acrylonitrile.

United Kingdom Pat. No. 993,498 relates to a process wherein bonded fiber fabrics are produced from fibers comprising homopolymers or copolymers of acrylonitrile containing at least 80 percent, preferably from 90 to 95 percent weight of acrylonitrile units, by applying a latent solvent to the fibers, making the fibers up into a web and bonding the web of fibers with latent solvent by activation. In this specification a latent solvent is defined as a liquid which normally does not dissolve particular fibers but which may be activated, usually by heating, to become a suitable solvent. Di-substituted formamides, propylene carbonate and sulfolane have been suggested as suitable latent solvents.

It has been found that sulfolane fails to effect appropriate bonding of fibers made from the modified polyacrylonitriles referred to hereinbefore, when applied as a latent solvent in accordance with the process described in United Kingdom Pat. No. 993,498.

However, it has now been found that these modified acrylonitrile fibers may quite satisfactorily be bonded when a sulfolanyl ether is used as the latent solvent. It has also been found that sulfolanyl ethers are good latent solvents for the handling of cellulose ester and chlorofibers.

Accordingly, the invention relates to a process for the production of bonded fiber fabrics in which a web of modified polyacrylonitrile fibers, cellulose ester fibers or chlorofibers, to which has been applied a normally liquid sulfolanyl ether, is heated to effect bonding of the fibers. The process comprises applying a normally liquid sulfolanyl ether to a web of fibers selected from the group consisting of modified polyacrylonitrile fibers, cellulose ester fibers and chlorofibers, and heating the web and sulfolanyl ether to effect bonding of the fiber.

Preferred sulfolanyl ethers are 3-sulfolanyl ethers, such as the isopropyl ether, n-butyl ether, isobutyl ether, tert-butly ether, n-hexyl ether, 2-ethyl-hexyl ether, n-octyl ether, phenyl ether, benzyl ether, toluyl ether, xylenyl ether, and isopropyl benzyl ether. Particularly preferred are the ethers derived from benzyl alcohol and aliphatic alcohols with from three to nine carbon atoms inclusive. In addition to the hydrocarbyloxy substituent the ethers may also contain other substituents such as alkyl groups of up to six carbon atoms or halogen atoms in the sulfolane nucleus. The term normally liquid" defines those ethers which are liquid at room temperature.

The sulfolanyl ethers may be applied to the fibers either before or after the fibers have been made up into a web. Normally they will be applied in amounts of from 1 to percent by weight, based on the weight of the fibers to be bonded, and preferably in amounts of from 5 to 20 percent by weight. The ethers can be used as such or as aqueous solutions containing water in amounts of up to 80 percent by weight, based on the total weight of the solutions. Heating of the fibers to effect bonding by the action ofthe sulfolanyl ether is usually done at temperatures above 60 C. for a period of from 0.5 to 20 minutes. It is to be understood that the temperature adopted for heating the fibers should always remain below the temperature at which the fiber begins to lose its useful properties. Preferred temperatures for bonding modified polyacrylonitrile fibers are from to 120 C. Preferred temperatures for bonding chlorofibers are from 60 to 80 C.

Fibers of particular interest are those from a modified polyacrylonitrile obtained by copolymerization of acrylonitrile and vinylidene chloride or vinyl chloride as the unsaturated comonomer. Such fibers are commercially available. Suitable cellulose ester fibers are cellulose acetate, diacetate or triacetate and cellulose acetobutyrate. Such fibers are also commercially available. Suitable chlorofibers are fibers of polyvinylchloride and polyvinylidenechloride or copolymers of vinyl chloride or vinylidene chloride with at least 50 percent weight of a suitable comonomer. Advantageously, cellulosed diacetate fibers are bonded by heating at temperatures of from 75 to C. Particularly suitable heating temperatures for bonding triacetate fibers are from to l60C.

The invention is illustrated by means of examples.

EXAMPLE I A 6 6 0, 5-inch web of 9-denier fibers made from a commercially available copolymer of acrylonitrile was placed in a wooden frame with a removable wire mesh at the back and front. 10 percent weight of isopropyl-3-sulfolanyl ether was applied to the web by spraying. To effect bonding, the web was heated by passing hot air through the web at a temperature of 90 C. for a period of 10 minutes. The bonding effect obtained was investigated by feel, visual appearance and by microscopic inspection and it was shown that the bonding of the fibers in the web was satisfactory.

Similar experiments were carried out using other 3-sulfolanyl ethers and 3-,4- or 9-denier fibers. A satisfactory bonding was obtained in each experiment. The fibers and the ethers tested are summarized in table I. In table I the fiber designated A" was a commercially available copolymer of acrylonitrile, B was a modacrylic fiber which was a copolymer of 60 percent acrylonitrile and 40 percent vinyl acetate and C was a copolymer of 40 percent acrylonitrile and 60 percent vinyl chloride.

TABLE 1 Fiber Denier Ether Benzyl Benzyl lsopropyl n-Propyl n-Butyl t-Butyl lsobutyl Am yl n-Hexyl lsopropyl lsopmpyl n-Butyl lsobutyl EXAMPLE [I Similar experiments were carried out using several 3-sulfolanyl ethers and 8-denier filament diacetate (D), B-denier triacetate fiber (E) and 4.5-denier fiber (F). A satisfactory bonding was obtained in each experiment. The fibers and the 70 ethers tested are summarized in the table below as well as the bonding temperatures employed (C.). The remaining conditions of these experiments were as described in example I.

TABLE ll Fiber Temperature Ether "D" 80 Benzyl D 90 Benzyl D 85 lsopropyl E" 125 n-Butyl "E 130 lsopropyl "F" 70 Benzyl F" 65 n-Butyl F" 75 lsopropyl EXAMPLE "I In two continuous runs l06-cm. wide laps are made from 9- denier modacrylic staple fibers with a fiber length of 6 cm. Before entering a card, isopropyl sulfolanyl ether is added to the fibers by drip-feeding in amounts of and percent weight (on fiber) respectively. The carded laps are transformed into a wadding with a weight of 100 g./m. by cross-laying the laps and the waddings are then passed through an oven to efiect heating at temperatures of 100 and 1 15 C. respectively.

An adequate bonding of the fibers in the waddings was obtained in each of these two runs.

We claim as our invention:

1. A process for the production of bonded fiber fabrics which comprises applying a normally liquid sulfolanyl ether to a web of fibers selected from the group consisting of modified polyacrylonitrile fibers, cellulose ester fibers and cholorfibers; and heating said web with said sulfolanyl ether to effect bonding ofsaid fibers.

2. A process as claimed in claim 1, in which the ether is a 3- sulfolanyl ether.

3. A process as claimed in claim 2 in which the ether is 3- benzyl sulfolanyl ether.

4. A process as claimed in claim 1 in which the ether is a 3- alkyl sulfolanyl ether in which the alkyl group contains from three to nine atoms.

5. A process as claimed in claim 4, in which the ether is 3- isopropyl sulfolanyl ether.

6. A process as claimed in claim 1, in which modified polyacrylonitrile fibers are heated at a temperature of from to 120 C.

7. A process as claimed in claim 1, in which cellulose diacetate fibers are heated at a temperature from 75 to C.

8. A process as claimed in claim 1, in which cellulose triacetate fibers are heated at temperatures of from to 9. A process as claimed in claim 1, in which chlorofibers are heated at a temperature of from 60 to 80 C. 

2. A process as claimed in claim 1, in which the ether is a 3-sulfolanyl ether.
 3. A process as claimed in claim 2 in which the ether is 3-benzyl sulfolanyl ether.
 4. A process as claimed in claim 1 in which the ether is a 3-alkyl sulfolanyl ether in which the alkyl group contains from three to nine atoms.
 5. A process as claimed in claim 4, in which the ether is 3-isopropyl sulfolanyl ether.
 6. A process as claimed in claim 1, in which modified polyacrylonitrile fibers are heated at a temperature of from 85* to 120* C.
 7. A process as claimed in claim 1, in which cellulose diacetate fibers are heated at a temperature from 75* to 95* C.
 8. A process as claimed in claim 1, in which cellulose triacetate fibers are heated at temperatures of from 110* to 160* C.
 9. A process as claimed in claim 1, in which chlorofibers are heated at a temperature of from 60* to 80* C. 